One well known form of harrowing or cultivating farm land is to mount a plurality of dished discs upon a shaft carried from a suitable support frame and to tow the frame and thus the associated discs behind a tractor in such manner that the discs are able to cut into the upper layers of the soil and in so doing break down such layers into a more friable or loosened condition.
It is also well known that an important factor in relation to farm cultivation is that a cultivation process should not unduly compact the soil and should, if possible, produce an overall uniform result.
Thus in relation to harrowing it is an important requirement that the soil should be as uniformly cultivated and that, in addition, the harrowing discs used should be able to penetrate the ground in as uniform manner as possible.
In other words, it is important to ensure that during harrowing the operational conditions are such that the harrow discs cut the soil rather than merey sliding or slipping over the surface.
In relation to the harrowing operation it is important to understand that the usefulness of a harrow having rotatable discs as the harrow tools differs from soil condition to soil condition. For example, the usefulness for working upon a heavy soil, i.e., clay or water laden soil may well be quite different from operation in light, i.e., sandy, soils.